Another alternative to toxic chemical fungicides is the following: 1 heaping teaspoon of baking soda, 1 tablespoon of horticultural oil (use a summer oil such as SunSpray, not dormant oil), and1/2 teaspoon of insecticidal soap in one gallon of water. Shake well. The oil helps the baking soda stick, and the soap keeps the oil emulsified. This is useful for powdery mildew, downy mildew and botrytis, all fungal diseases. The picture is of downy mildew on a begonia. Water your plants thoroughly a couple of days before using the spray. Repeat once a week until all signs of infection are gone, and as a preventative on suseptible plants. After several weeks of using this spray it would be wise to flush the soil with lots of water to remove excess sodium which will cause the soil to turn alkaline.
